Personal communications most often take the form of one of two types of traffic, "continuous" traffic and "burst" traffic. Continuous traffic refers to lengthy communications message transmissions and burst traffic refers to short (communications burst) message transmissions. Both uni-directional and bi-directional continuous message traffic communications systems are known in the art.
The long message nature of continuous message traffic necessitates the establishment of multiple and separate bi-directional communications channels between users and uni-directional channels to decrease or eliminate instances of signal interference or confusion between communications. These channels are either wireline channels to fixed locations or radio frequency channels to service location areas. The short message nature of burst communications is well suited to single channel communications systems. A single radio frequency channel can be used to efficiently handle uni-directional burst communications for a plurality of subscribers as such communications transmissions are unlikely to, or can be controlled not to occur at the same time (otherwise, transmission signal interference would result).
Bi-directional burst communications, on the other hand, have been historically too complex to implement over a single radio frequency channel due to the difficulty in controlling overall system communications timing between a plurality of system subscribers where the timing of both signal transmissions and signal responses between all subscribers tend to be too small and too critical to handle the required capacity in a practical and cost effective fashion. Thus, bi-directional communications must be accurately controlled to avoid simultaneous transmission and signal interference and confusion on the channel. Until now, communications technology and system architecture has been unsuccessful in solving the timing problems presented by single channel bi-directional burst communications between a plurality of subscribers.
Bi-directional burst traffic networks, if available, could be advantageously used to enhance the operational capabilities of both burst and continuous traffic systems, such as paging, cellular telephonic and wireline telephonic systems, to provide a comprehensive personal communications system. Bi-directional burst traffic can be used as an out-of-band signal to locate subscribers and provide notice of in-band personal communications in a manner similar to a paging service. Out-of-band burst communications of a command, control and management nature are useful for controlling in-band continuous telephonic communications as such out-of-band burst communications signals are accessible independent of location. One such system for using bi-directional burst type traffic is disclosed in commonly assigned, co-pending U.S. application for patent Ser. No. 07/723,169.
The issue raised by a bi-directional burst communications system as described above is how are the bi-directional communications going to be managed and carried over a single radio frequency channel. As mentioned above, current communications technology does not permit bi-directional multiple subscriber bursts over a single channel due to signal interference and confusion concerns. Time division multiplexing of the communications over the single channel (similar to wireline telephonic communications) is an alternative solution; however, each subscriber would require their own time slot for communications. This is an impractical solution when communication is desired over a wide service area with a substantial number of subscribers. As the number of time slots in a time division multiplexed system increases to handle additional subscribers, proportional changes in the width of the slot or length of the time cycle occur which limit the amount of information that can be communicated.
A continuous bi-directional communications system addresses the signal interference and confusion problem of a single channel communications network by using assigned frequencies (multiple channels) to carry conversation within limited geographic areas. However, such a configuration consumes a significant portion of the communications spectrum, even with frequency channel reutilization, and is an inefficient means for carrying short bi-directional burst transmissions. Moreover, an equivalent wide spectrum for bi-directional burst communications is not currently available and is unlikely to be provided by the Federal Communications Commission through frequency assignment or reallocation.
For the practical, administrative and technological reasons described above, individual frequency channel assignment (frequency multiplexing as with cellular continuous communications) and individual time slot assignment (time division multiplexing as with wireline continuous communications) are not available solutions addressing the timing concerns of, and the need for bi-directional burst communications. Accordingly, there is a need for a method and system network for enabling bi-directional burst communications to occur over a single radio frequency channel having a limited bandwidth.